1. Field of the Invention
The present invention relates to a circuit board and a method of fabricating the same. In particular, the present invention relates to a circuit board having a conductive joint column and a method of fabricating the same.
2. Description of Related Art
Generally speaking, a conventional circuit board for carrying and electrically connecting a plurality of electronic devices is mainly composed of a plurality of circuit layers and a plurality of dielectric layers alternately stacked. Each circuit layer is formed by defining a copper foil in a patterning process. Each dielectric layer is disposed between the adjacent circuit layers for isolating the circuit layers. In addition, the stacked circuit layers are electrically connected to each other through conductive vias. Moreover, various electronic devices (for example, active or passive devices) may be further disposed on a surface of the circuit board, and electrical signal propagation among those electronic devices is achieved by internal circuits of the circuit board.
Please refer to FIG. 1 which is a schematic cross-sectional view of a conventional circuit board. A conventional circuit board 100 includes a dielectric layer 110, a circuit layer 120, a patterned solder mask layer 130 and a plurality of solder balls 140. The circuit layer 120 having a plurality of pads 122 is disposed on the dielectric layer 110. The patterned solder mask layer 130 is disposed on the dielectric layer 110 to cover a portion of the circuit layer 120. The patterned solder mask layer 130 has a plurality of openings 132 to expose the pads 122, respectively. In addition, the solder balls 140 are disposed on and electrically connected to the pads 122, respectively.
However, during the fabrication of the conventional circuit board 100, the openings 132 may not be precisely aimed at the pads 122 respectively when the patterned solder mask layer 130 is formed. Thereby, the patterned solder mask 130 may overly cover a part of the pads 122 (for example, the right pad 122 depicted in FIG. 1). Accordingly, as the solder balls 140 are formed on the pads 122 respectively, an area of junctions between parts of the solder balls 140 (for example, the right solder ball 140 depicted in FIG. 1) and the corresponding pads 122 (for example, the right pad 122 depicted in FIG. 1) is reduced, such that the reliability of bonding between the parts of the solder balls 140 and the corresponding pads 122 is decreased.